Infinitives as adverbial or adjectival

I take them as adjectival.
The only verb to be modified is "to be."

A counter example would be: My brother is continually late for work.

I'd say "continually" here is adverbial, because it modifies "is."

My brother was always slow to learn. "Always" is adverbial. The infinitive modifies "slow."

But in the sentence "My brother was slow to react" , "to react" modifies the adjective "slow".
So, shouldn't "to react" be adverbial ?

To my ear, they answer the question "How?" or "In what way?", not the question "What kind of?" so they would be adverbial.

Quick in what way? Quick to learn. They learn quickly.

Slow in what way? Slow to react. He reacts slowly.

CJ

Debpriya De"My brother was slow to react" , "to react" modifies the adjective "slow".

My interpretation of "to react" is an "infintive phrase" which is adverbial by nature.

Hmmm. This confuses me. I guess you can say that adverbs have two functions:
1. to modify verbs
2. to modify adjectives

My brother is slow. "Slow" is the adjective complement of the verb, "to be." Since "to react" modifies the adjective "slow," I guess it has to be an adverb.

For some reason, when someone asks if an expression is adverbial, I think only in terms of fu

dimsumexpress an "infintive phrase" which is adverbial by nature.

You do not have the right to park here. ??
He was the first to reach the summit. ??

Avangimmm. This confuses me. I guess you can say that adverbs have two functions:
1. to modify verbs
2. to modify adjectives

But adverbial phrase can modify another phrase or the main clause.
i.e. John is a lot of fun [to be with].

dimsumexpress which modifies the main clause. And that's how I approach adverbials.

I agree with you that when something modifies the whole clause, it's adverbial. The verb is sort of the default king of the clause.

Avangithe right to park here. ??
He was the first to reach the summit. ??

I am not sure if you are disagreeing with my previous post, or simply asking for additonal explanations. Anyhow, (right or wrong) I'd say, the underlined functioned adverbially. Here it explains:

Perhaps I misunderstood what you mean by, an infinitive phrase is adverbial by nature.

You do not have the right to park here. ??
He was the first to reach the summit. ??

I guess you're also affirming that these infinitive phras